Dr. Daniel Stephenson, Joey Boudreaux, and Dr. Jim Griffin
Over the last month, many individuals have called about the preharvest interval of 15 days for paraquat (Gramoxone SL, Parazone, others. ) applications. Many Louisiana soybean producers are not willing to wait 15 days after paraquat application for harvest. As a consequence, producers are seeking an alternative for desiccation that will allow for earlier harvest. Sodium chlorate is an option, but many have chosen to ignore this option mainly due to the excellent results obtained with paraquat.
Due to the enforcement of the paraquat 15 day preharvest interval, sodium chlorate use has increased. A recent article written by Drs. Ronnie Levy and Jim Griffin (Soybean Harvest Aid Recommendations for 2012) provides information on use of Aim 2EC, paraquat, and sodium chlorate as harvest aids. This article was disseminated on Friday, August 17th.
One of the main questions being asked concerns the tank-mixing of sodium chlorate and Aim 2EC. We don’t have any data on this treatment, but we are currently investigating it. Joey Boudreaux and Dr. Griffin published an article in Weed Technology in 2011 entitled “Application Timing of Harvest Aid Herbicides Affects Soybean Harvest and Yield” that will provide some insight on this question. The research discussed in the article is the data from which Dr. Griffin bases the application timing of a soybean harvest aid. Application timing of harvest aid is discussed in the article published by Drs. Levy and Griffin.
In the Boudreaux and Griffin article, paraquat at 0.25 lb ai/A, paraquat + Aim 2EC at 0.8 oz/A, and sodium chlorate at 6 lb/A were evaluated. They found no differences between any of these treatments in respect to the level of dessication or rate of dessication. That is to say that soybeans were ready for harvest at the same time regardless of whether paraquat alone, paraquat plus Aim, or sodium chlorate were applied. This also shows that soybean desiccation with paraquat was not affected either positive or negative with the addition of Aim.
Although their research did not specifically investigate sodium chlorate tank-mixed with Aim 2EC, it did show that sodium chlorate at 6 lb/A (1 gallon/A of a 6 lb/gallon sodium chlorate) was as effective as was paraquat at 0.25 lb ai/A (1 pt/A of Gramoxone SL or 10.7 oz/A of a generic 3 lb/gal paraquat) for desiccation of soybean. With sodium chlorate the label states that application should be made 7 to 10 days before anticipated harvest date.